IndexFaces

Detects faces in the input image and adds them to the specified collection.

Amazon Rekognition doesn't save the actual faces that are detected. Instead, the underlying
detection algorithm first detects the faces in the input image. For each face, the
algorithm
extracts facial features into a feature vector, and stores it in the backend database.
Amazon Rekognition uses feature vectors when it performs face match and search operations
using the
SearchFaces and SearchFacesByImage
operations.

If you're using version 1.0 of the face detection model, IndexFaces
indexes the 15 largest faces in the input image. Later versions of the face detection
model
index the 100 largest faces in the input image.

If you're using version 4 or later of the face model, image orientation information
is not returned in the OrientationCorrection field.

To determine which version of the model you're using, call DescribeCollection
and supply the collection ID. You can also get the model version from the value of
FaceModelVersion in the response
from IndexFaces

If you provide the optional ExternalImageID for the input image you
provided, Amazon Rekognition associates this ID with all faces that it detects. When
you call the ListFaces operation, the response returns the external ID. You can use this
external image ID to create a client-side index to associate the faces with each image.
You
can then use the index to find all faces in an image.

You can specify the maximum number of faces to index with the MaxFaces input
parameter. This is useful when you want to index the largest faces in an image and
don't want to index
smaller faces, such as those belonging to people standing in the background.

The QualityFilter input parameter allows you to filter out detected faces
that don’t meet the required quality bar chosen by Amazon Rekognition. The quality
bar is based on a
variety of common use cases. By default, IndexFaces filters detected faces. You
can also explicitly filter detected faces by specifying AUTO for the value of
QualityFilter. If you do not want to filter detected faces, specify
NONE.

Note

To use quality filtering, you need a collection associated with version 3 of the
face model. To get the version of the face model associated with a collection, call
DescribeCollection.

Information about faces detected in an image, but not indexed, is returned in an array
of
UnindexedFace objects, UnindexedFaces. Faces aren't
indexed for reasons such as:

The number of faces detected exceeds the value of the MaxFaces request
parameter.

The face is too small compared to the image dimensions.

The face is too blurry.

The image is too dark.

The face has an extreme pose.

In response, the IndexFaces operation returns an array of metadata for
all detected faces, FaceRecords. This includes:

The bounding box, BoundingBox, of the detected face.

A confidence value, Confidence, which indicates the confidence that the
bounding box contains a face.

A face ID, FaceId, assigned by the service for each face that's detected
and stored.

An image ID, ImageId, assigned by the service for the input image.

If you request all facial attributes (by using the detectionAttributes
parameter), Amazon Rekognition returns detailed facial attributes, such as facial
landmarks (for
example, location of eye and mouth) and other facial attributes like gender. If you
provide
the same image, specify the same collection, and use the same external ID in the
IndexFaces operation, Amazon Rekognition doesn't save duplicate face metadata.

The input image is passed either as base64-encoded image bytes, or as a reference
to an
image in an Amazon S3 bucket. If you use the AWS CLI to call Amazon Rekognition operations,
passing image bytes isn't supported. The image must be formatted as a PNG or JPEG
file.

This operation requires permissions to perform the rekognition:IndexFaces
action.

An array of facial attributes that you want to be returned. This can be the default
list of attributes or all attributes. If you don't specify a value for Attributes
or if you specify ["DEFAULT"], the API returns the following subset of facial
attributes: BoundingBox, Confidence, Pose,
Quality, and Landmarks. If you provide ["ALL"], all
facial attributes are returned, but the operation takes longer to complete.

If you provide both, ["ALL", "DEFAULT"], the service uses a logical AND
operator to determine which attributes to return (in this case, all attributes).

The maximum number of faces to index. The value of MaxFaces must be greater
than or equal to 1. IndexFaces returns no more than 100 detected faces in an
image, even if you specify a larger value for MaxFaces.

If IndexFaces detects more faces than the value of MaxFaces, the
faces with the lowest quality are filtered out first. If there are still more faces
than the
value of MaxFaces, the faces with the smallest bounding boxes are filtered out
(up to the number that's needed to satisfy the value of MaxFaces). Information
about the unindexed faces is available in the UnindexedFaces array.

The faces that are returned by IndexFaces are sorted by the largest face
bounding box size to the smallest size, in descending order.

MaxFaces can be used with a collection associated with any version of
the face model.

A filter that specifies how much filtering is done to identify faces that are detected
with low quality. Filtered faces aren't indexed. If you specify AUTO, filtering
prioritizes the identification of faces that don’t meet the required quality bar chosen
by
Amazon Rekognition.
The
quality bar is based on a variety of common use cases. Low-quality
detections can occur for a number of reasons. Some examples are an object that's misidentified
as a face, a face that's too blurry, or a face with
a
pose that's too extreme to use. If you specify NONE, no
filtering is performed. The default value is AUTO.

To use quality filtering, the collection you are using must be associated with version
3 of the face model.

If your collection is associated with a face detection model that's later
than version 3.0, the value of OrientationCorrection
is always null and no orientation information is returned.

If your collection is associated with a face detection model that's
version 3.0 or earlier, the following applies:

If the input image is in .jpeg format, it might contain exchangeable image file format
(Exif) metadata
that includes the image's orientation. Amazon Rekognition uses this orientation information
to perform
image correction - the bounding box coordinates are translated to represent object
locations
after the orientation information in the Exif metadata is used to correct the image
orientation.
Images in .png format don't contain Exif metadata. The value of OrientationCorrection
is null.

An array of faces that were detected in the image but weren't indexed. They weren't
indexed because the quality filter identified them as low quality, or the
MaxFaces request parameter filtered them out. To use the quality filter, you
specify the QualityFilter request parameter.